(1) Field of the Invention
The present invention relates to switch circuits with the ability to control latch-up due to a parasitic element.
(2) Description of the Related Art
Japanese Patent Application Publication Nos. 2003-224244, 2000-224298, and 2004-350127 each disclose a conventional switch circuit in which bidirectional conductivity is possible.
Japanese Patent Application Publication No. 2003-163589 discloses a semiconductor device in which a transistor and a Schottky barrier diode are provided on the same chip. In the Schottky barrier diode, the drain electrode of the transistor is connected to a cathode electrode, and the source electrode of the transistor is connected to an anode electrode. By providing this semiconductor device with a Schottky barrier diode, the occurrence of a minority carrier in a PN junction face between a drain diffusion layer and an N-well region of the transistor is suppressed, so that it is possible to prevent the operation of a parasitic transistor present on the substrate on which the semiconductor device is formed.
However, the transistors used to configure the switch circuit disclosed in Japanese Patent Application Publication Nos. 2003-224244, 2000-224298, and 2004-350127 have PN junction faces between each of the diffusion layers that function as the drain or the source, and the well regions in which these diffusion layers are formed, and when a forward bias voltage is applied to these PN junction faces, minority carrier injection occurs. When minority carrier injection occurs, there is a risk that latch-up will occur due to a parasitic thyristor present on the substrate on which the switch circuit is formed.
Also, with the semiconductor device disclosed in Japanese Patent Application Publication No. 2003-163589, it is possible to suppress the occurrence of a minority carrier by mitigating the forward bias current that occurs at the drain-side PN junction face, but when the direction of the current between the source and the drain has been reversed, it is not possible to suppress the occurrence of a minority carrier at the source-side PN junction face.
In order to address these problems, it is an object of the present invention to provide a switch circuit, a diode, and a transistor, in which bidirectional conductivity is possible, and with the ability to control the occurrence of latch-up due to a parasitic element.